The mission of this Program is to prepare a cadre of outstanding cancer epidemiologists through rigorous academic training in research methodology and the epidemiology and biology of cancer, and mentored research. Trainees supported through the Molecular & Genetic Epidemiology Sub-program receive additional training in the application of molecular genetic techniques to epidemiologic research. A distinguished faculty provides a variety of substantial opportunities for research experience. There are three types of trainees: Doctoral Candidates in Epidemiology includes pre-doctoral candidates either with or without a prior doctoral degree (generally clinicians) who undertake 2-3 years of coursework, in addition to research, in the course of earning a doctoral degree in Epidemiology; Clinical Researchers include physicians with specialty training in cancer preparing for careers in clinical epidemiology who undertake a one year Master's degree program in methodology followed by a year of research; and Post-doctoral Fellows who hold a prior doctoral degree in Epidemiology or in Biology and undertake mentored research (and with coursework if needed) in preparation for an academic career. Trainee positions are generally awarded for 2 or 3 years. The number of trainee positions requested includes 3-4 pre-doctoral and 1-2 post-doctoral Doctoral Candidates: 2 Clinical Researchers: 2 Post-doctoral Fellows with an additional 4 pre-doctoral Doctoral Candidates and 3 Postdoctoral Fellows in the Sub-program for a total of 16 trainees. The Program is based in the Department of Epidemiology of the Harvard School of Public Health. A dedicated molecular epidemiology laboratory is available. This proposal continues a long history of excellence in training in cancer epidemiology at Harvard University; the current training program is now in its 32nd year, with an outstanding record of achievement in training. RELEVANCE: Knowledge about cancer epidemiology - the study of the determinants and distribution of cancer in human populations - has grown exponentially. With major advances in methodology, cancer biology and genetics, the need for well-trained highly skills researchers and clinicians in this area has never been greater. We propose, through this training grant, to continue to provide high quality cancer epidemiology training to educate the next generation of outstanding scholars and public health researchers in this vital field.